Promising transparent and flexible thermoelectric modules based on p-type CuI thin films—A review

The state-of-the-art thermoelectric technology owns a unique capability of direct, noise-free, and efficient conversion of waste heat into valuable electricity. The conventional thermoelectric generators are complex and expensive in fabrication, which restricts their use in wearable and miniaturized electronics to fulfill the current and rapid growth in demands for sufficient self-powered energy harvesters. Herein, this comprehensive review paper highlights the promising and next-generation thermoelectric generators based on flexible, transparent, abundant, non-toxic, and lightweight p-type Copper Iodide (CuI) thin films. It introduces the principles of energy conversion within thin-film thermoelectric generators and the structure of p–n junction including the criteria in the selection of substrates, p-type and n-type materials, connecting electrodes, and modules designed to sustain its mechanical flexibility and optical transparency. This review underlines the morphology and properties of CuI thin-film thermoelectric generators to figure out the latest trends in advanced synthesis and characterization techniques. It draws attention to its promising applications in wearable biosensing, energy harvesting, and smart miniaturized electronics. It discusses also the challenges and prospects in boosting the thermoelectric performance of CuI thin-film generators. This targeting to exceed the unity in its Figure-of-Merit (ZT) values for excellent output power generation, large-scale production for commercialization, and long-term stability for reliable thermoelectric applications.